In electronic circuit design, simulations are often performed before physical prototypes are constructed. During simulations involving electronic package and/or multi-layer printed circuit board (PCB), physical systems are usually represented or approximated by mathematical models, and the mathematical models often contain high-order linear- and/or non-linear systems, which are complicated and difficult (or time-consuming) to solve. Accordingly, there is a need to effectively reduce the order of mathematical models to improve speed and efficiency.